The Retreat seminar building is used for management training. The structure is designed to be fully energy-autonomous, independent of external power supply. In addition, the design combines traditional and modern requirements. With only 25% higher investment costs, the energy costs are 40-50% under conventional buildings. Energy is supplied via a solar system and a biogas plant, while good building insulation and an underground air tunnel system provide comfortable temperatures. Waste water from the kitchen and the toilet system is treated in a natural reed facility and used for watering. The building saves 570 tons of CO² annually.